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Want to eat large amounts of food without expanding your waistline? Eat these nutrient-dense, zero-calorie foods — from citrus fruits to bell peppers — to be fit and healthy. Photo courtesy of Shutterstock

Going to the gym to maintain a healthy weight is only half the battle. The other half is following a nutrition-dense and well-balanced diet. Counting calories can get mentally, and even physically, exhausting totaling up all the foods in one day. While most of us want to literally have our cake and eat it, too — especially one with zero calories — this remains a food fantasy. However, there are foods that cost us nothing to eat, calorie-wise, known as free foods, or almost free foods.

Despite popular belief, not all zero-calorie foods are “rabbit food.” There are fruits, snacks, and even frozen desserts that can make even those with the most hard-to-please taste buds salivate. While there is no such thing as negative calories, since calorie is a measurement of energy, there are foods that do require more energy for your body to digest than they provide you with. These foods lead to greater nutrient intake, and help you feel full, without the risk of weight gain.

Dieters should not solely rely on these foods. “They're necessary but not sufficient for health. They have no protein or fat (for the most part), both of which are critical for health maintenance,” Jackie Keller, founding director of NutriFit, board certified Health Coach, and former certified trainer in Los Angeles, Calif., who has worked with celebrities from Angelina Jolie to Bryan Cranston, told Medical Daily.

To eat large quantities of food, without expanding your waistline, add these six zero-calorie foods to your diet today:

1. Apples

An apple a day really does keep the doctor away, when it comes to weight management. This fruit is often referred to as a “negative calorie” food because the body burns more calories to consume and digest it, compared to how much the food contains. To get the most nutrients from an apple, do not peel off the skin. A 2012 study found the waxy coats on apples contain fiber that boosts the metabolism, along with ursolic acid, which prevents weight gain.

2. Asparagus

This vegetable is considered to be one of nature’s diuretics that helps flush water out of the body, acting as a fat repellent. A half-cup of asparagus only amounts to 20 calories, providing you with heavy doses of vitamins K, A, and B. Asparagine, an alkaloid chemical in asparagus, helps breaks down fat cells and can also help reduce overall body fat. The vegetable also acts as an anti-aging agent that protects against cancer and can even reduce pain and inflammation.

3. Bell peppers

These colorful peppers, red, green, yellow, and orange are all excellent sources of vitamin B6, vitamin C, and folic acid. These vegetables contain phytochemicals that are known to protect against heart disease, cancer, stroke, and cataracts. Red bell peppers contain 250 percent of the daily recommended intake of vitamin C, 75 percent of vitamin A, and 10 percent of fiber, according to Fruits & Veggies More Matters.

4. Cucumbers

Snacking on cucumbers is a good and clever way to sneak in some water in your diet. This vegetable is the perfect water-rich, negative-calorie food. Cucumbers are so sparse in calories they fill your stomach with water, reducing the amount of space left for other foods, therefore triggering the “stop eating” signals in the brain. Vanessa Castro, nutritionist and personal trainer in Florida, told Medical Daily, “Water is great because often times, we confuse thirst for hunger. Increasing your water intake can not only decrease your appetite but also make your skin look better and may even help with cellulite!”

5. Leafy Greens

A salad with plenty of green variety can help keep your weight at bay. Keller suggests to stick with “lettuces and other dark leafy greens” to increase your vitamin A, C, and K intake. A 2007 study found eating 3 ounces of watercress daily actually increases lutein and beta-carotene — cancer-fighting antioxidants. Leafy greens also contain plenty of fiber along with vitamins, minerals, and plant-based substances that can help protect you from heart disease, diabetes, and possibly cancer. They have powerful immune-boosting phytochemicals.

These zero calorie foods should not be used as a major source of your diet. “[R]eplacing other foods with zero calorie foods like green tea can help reduce your caloric intake and ultimately help you achieve your weight loss goals,” Castro said. It can be dangerous to remain on a low-calorie diet on a regular basis, so it’s important to consume enough calories to support your daily activity.